#include <stdio.h>
void to_binary(unsigned long n);
int main(void)
{
    unsigned long number;
    printf("Enter an integer(q to quit): \n");
    while(scanf("%ul", &number) == 1)
    {
        printf("Binary equivalent: ");
        to_binary(number);
        putchar('\n');
        printf("Enter an integer(q to quit): \n");
    }
    printf("Done.\n");
    getchar();
    getchar();
    return 0;
}

void to_binary(unsigned long n)
{
    int r;
    r = n % 2;
    if(n >= 2)
        to_binary(n / 2);
    putchar('0' + r);
    
    return;
}
